Pressure sensors have various applications. As an example, pressure sensors have been used to determine parameters (e.g., level, volume, mass) of liquid in a pressurized liquid storage tank. FIGS. 1-4 show various existing pressure sensor configurations for this application.
FIG. 1 shows a pressure sensor configuration 100 comprising a pressurized tank 102 coupled to a pressure sensor 104 and a differential pressure sensor 106 via pressure piping. The pressure sensor 104 measures pressure at the top (HI) port of the tank 102 (compared to vacuum or atmospheric pressure) and the differential pressure sensor 106 measures a difference in pressure between the HI port and LO port of the tank 102. The pressure measurements from the pressure sensor 104 and the differential pressure sensor 106 are provided to an electronics/communication module 108 via electrical wiring. The electronics/communication module 108 processes the pressure measurements from the pressure sensor 104 and the differential pressure sensor 106 and/or forwards these pressure measurements to a remote computer for processing.
In FIG. 2, a pressure sensor configuration 200 is shown with a combo pressure/differential pressure (PDP) sensor 204 coupled to the tank 102 via pressure piping. The combo PDP sensor 204 comprises a pressure sensor and a differential pressure sensor integrated into a single unit to reduce cost and complexity. The combo PDP sensor 204 measures pressure at the HI port of the tank 102 (compared to vacuum or atmospheric pressure) and measures a difference in pressure between the HI port and the LO port of the tank 102. The pressure measurements from the combo PDP sensor 204 are provided to an electronics/communication module 208 via electrical wiring. The electronics/communication module 208 processes the pressure measurements from the combo PDP sensor 204 and/or forwards these pressure measurements to a remote computer for processing.
In FIG. 3, a pressure sensor configuration 300 is shown with the differential pressure sensor 106 coupled to the tank 102 via pressure piping. The differential pressure sensor 106 measures a difference in pressure between the HI port and the LO port of the tank 102. The pressure measurements from the differential pressure sensor 106 are provided to an electronics/communication module 308 via electrical wiring. The electronics/communication module 308 processes the pressure measurements from the differential pressure sensor 106 and/or forwards the pressure measurements to a remote computer for processing.
In the pressure sensor configuration 300, the differential pressure sensor 106 measures level. This sensor must handle the high static pressure of the tank, but the difference in pressure between the inputs may be limited to a lower pressure (eg twice the differential pressure range). This means that if a user connected the HI or LO port on the tank to the transmitter with the other side vented to atmosphere, the sensor would be damaged. Using a more complex differential pressure sensor or separate overpressure device is possible, but increases cost. Sensor configuration 300 is less costly than configurations 100 and 200, but does not provide measurement of tank pressure.
In FIG. 4, a pressure sensor configuration 400 is shown with two pressure sensors 104A and 104B coupled to the tank 102 via pressure piping. There is no differential pressure sensor in pressure sensor configuration 400. However, differential pressure is determinable by subtracting the pressure measurement of pressure sensor 104A from the pressure measurement of pressure sensor 104B (or vice versa). Using two pressure sensors 104A and 104B as in pressure sensor configuration 400 significantly magnifies measurement errors that occur due to temperature effect or other ambient effects because each pressure sensor 104A and 104B responds differently. For example, the differential pressure is calculated as: DP=PHI+EHI−(PLO+ELO), where PHI is the pressure at the HI port of the tank 102, EH, is the measurement error in PHI, PLO is the pressure at the LO port of the tank 102, and ELO is the measurement error in PLO. If EHI and ELO are large and in opposite directions, the accuracy of the differential pressure calculation suffers. The pressure measurements from the pressure sensors 104A and 104B are provided to an electronics/communication module 408 via electrical wiring. The electronics/communication module 408 processes the pressure measurements from the pressure sensors 104A and 104B and/or forwards these pressure measurements to a remote computer for processing.